The tool described is a WLAN (Wireless Local Area Network) scanner tool. WLAN scanner tools are designed to provide information about the wireless networks in a given area, including:

Signal Strength: They show the signal strength of all access points (APs) in the vicinity, which is crucial for understanding the coverage area and potential interference.

SSID Visualization: These tools display the SSIDs (Service Set Identifiers) of available networks, allowing users to identify different wireless networks easily.

Security Settings Information: WLAN scanner tools often show the type of security implemented on each network, such as WPA2, WEP, etc.

Frequency Band Filtering: They allow users to filter and view networks based on the frequency band (2.4 GHz or 5 GHz), which is useful for analyzing network distribution and planning.

While protocol analyzers, site survey utilities, and spectrum analyzers are also used in wireless networking, their functions are distinct from what is described:

Protocol Analyzers are more sophisticated and are used to capture and analyze network traffic.

Site Survey Utilities are used to map signal coverage and plan network layouts, often with more advanced features for detailed site surveys.

Spectrum Analyzers provide a detailed view of the frequency spectrum and non-Wi-Fi interference but don't typically focus on SSIDs or security settings.

Thus, the correct answer is D, a WLAN scanner tool, based on the functionalities described.